Rotary pump for power steering systems



April'22, 1969 T ET'AL 3,439,623

I I ROTARY PUMP FOR POWER STEERING SYSTEMS Filed on. 19, 1957 Sheet of s Fig 1 Q a Q I a l /Q 111 P- Fig. 2

Georg Dietrich Georg Kehrer Inventors by Attorney April 22, 19 69 I v G, D|ETR|H ET AL 3,439,623

- ROTARY PUMP FOR POWER STEERING SYSTEMS Filed Oct. 19, 1967 Sheet 2 of3 I Georg Kehrer Inventors Georg Dietrich by Attorney,

' Shee t 3 of s G. DIETRICH ET AL ROTARY PUMP FOR POWER STEERING SYSTEMS April 22, 1969 Filed Oct. '19, 1967 s m M W C C W s C m .nu S m Mime P 3 M W M .MMMM .mm m ww mm mm m @llll llllqllliw u n n u s 21- n J W F u w m 1|: I; w W m m H v E .0 h n u A was m cs/ M Georg Dietrich Georg Kehrer Inventors Attorney median rm-l/wmgv-pressure: 50 an? United States Patent Q 4 8 Int. Cl. FtMb 49708,- F040 3/00 US. Cl. 103-42 8 Claims ABSTRACT OF THE DISCLOSURE The disclosure relates to rotary vane pumps, particularly high pressure and high speed pumps for operating hydraulic motors of power booster systems. The invention features a pump having special passages and flow guidance means for auxiliary flow to the inlet chambers so that as the speed increases there will be an increased pressure at the inlet chambers which is proportional to the speed to effect an increase in intake flow to the pump rotor. Accordingly, cavitation due to high pump speeds which causes incomplete filling of the inlet chambers and the rotor cells is avoided. Full filling of the intake chambers is insured at extremely high speeds by an arrangement which increases intake to the pump chambers in proportion to the difference between the statics pressures actuated on the left and right side of a control valve piston, a function of pump speed within operating limits.

The prior art discloses, in US. Patent 2,853,023, a pump housing channel arrangement intended to overcome cavitation, and, in US, Patent 2,544,988 a flow regulating valve responsive to pump speed is disclosed which provides intake flow control as a function of the speed. However, both of the prior art devices fail to perform satisfactorily in installations where very high flow rates are required and wherein cavitation and ineflicient pump operation occurs.

Attention is called to the aforementioned Patent 2,853,023, col. 5, lines 4 through 10, which sets forth information concerning cavitation; thus cavitation is the result of operating a pump above a critical speed such that insuflicient fluid flows into the intake chambers and the rotor is only partially filled. Such phenomenon also causes increased noise and is, of course, highly undesirable.

The present invention overcomes the drawbacks of the prior art without increasing the conduits or channels of the pump housing in size, an important aspect of the invention because of the compactness required for the components of modern automobile engines and vehicles.

Briefly, the invention comprises the provision of a valve housing having a vane type rotor and a cam ring, i.e., a stator, together with check plates or sealing plates therein and a bypass valve whereby outlet pressure actuates the valve in order to provide a regulated amount of fluid to bypass from the outlet chambers to the inlet chambers to increase flow to the suction chambers, with increased pump speed, The arrangement just described is generally conventional, and heretofore known, as disclosed in prior art. However, the instant invention provides pumping etiiciency by improving the conventional construction to the extent of furnishing a specially shaped bypass channel for the bypass of fluid from the regulating bypass valve to the intake chambers. Thus the bypass channel is a noncircular channel having flow characteristics of a channel having a cross flow contour, i.e., the cross section, of an equilateral triangle which contour would be the ideal channel but which would be very difficult to machine into the housing of the pump. By arranging such an approximately triangular bypass channel as the outlet port of the bypass valve so as to direct flow from an apex, or an approximate apex, of the channel towards a flow director, there is a split or divided flow around the cam ring and into the intake chambers. Such flow going in both directions uniformly fills the chambers from a point at which the flow divider is located. A channel shaped as described is superior to a conventional circular channel since a circular channel serving as a valve port cannot control flow as a constant in proportion to the differential pressure which actuates the valve, as later explained.

A particular constructional feature of the invention resides in the fact that the flow divider is a support for the cam ring and by utilizing two additional formations identical to or similar to such flow divider, a three point suspension or support for the cam ring is afforded within the housing of the pump. Such a construction permits the elimination of dowel pins which are normally used to support the cam ring, except for a single dowel pin utilized in the invention to prevent rotation of the cam ring. The elimination of the dowel pins improves the performance of the pump by substitution of the three support segments, one of which serves as a flow divider.

Other features and advantages of the invention will be described in connection with the appended drawing in which:

FIGURE 1 is a cross sectional elevation of a pump incorporating the features of the invention;

FIGURE 2 is a section through II-II of FIGURE 1;

FIGURE 3 is a section through IIIIII of FIGURE 1;

FIGURE 4 is a section through IVIV of FIGURE 1;

FIGURE 5 is a section through VV of FIGURE 3; and

FIGURE 6 is a graph showing the improved performance of the invention in comparison with a conventional pump.

Referring to the drawing, there is disclosed a pump housing 2 which supports a rotary shaft 1 on which is mounted the pump rotor 4 having radially slidable vanes 7 and which rotor rotates within a stator or cam ring 5, all in the usual manner. There is also disclosed the sealing plates or check plates 6 and 6' maintained in sealing engagement with the rotor and stator by a spring backed by the cover plate 3 as well as by outlet pressure to which their outer faces are exposed. Sealing rings 18 are utilized in the usual manner for sealing the plates 6 and 6' Within the housing.

Particular attention is called to the mounting of the stator 5. It will be noted that the housing provides support for the stator, with a three point support, comprising integrally cast radially protruding segments 12, 12' and 12", seen in radial view on FIGURE 1. Such segments are an integral part of the housing and have smoothly finished surfaces 19, 19 and 19", respectively, which abut the periphery of the stator.

A single dowel pin 11, as seen on FIGURES 1 and 3, passes through the stator and sealing plates and into the housing for the purpose of keying these members together so that there will he no relative rotation therebetween. The dowel pin 11 does not effect a support for the stator, the stator being supported by the generally triangular and streamlined segments 12, 12' and 12" which extend longitudinally across the periphery of the stator approximately one-third the way as indicated in FIGURE 5.

The housing is provided with an inlet 15 (FIGURES 1 and 2) which conducts fluid to a suction bore 13, the bore 13 terminating perpendicularly in inlet channel 14 which leads to inlet chambers 8 and 8' peripherally surrounding the major portion of the stator ring and fashioned to permit flow lngitudinally into the cells between adjacent vanes 7. Outlet chambers 9 and 9 are provided which connect to pressure chamber 9" to the housing outlet 16 and a bypass 16'.

A pressure responsive bypass control valve actuatable by outlet pressure is indicated at 10 in FIGURES 1, 3 and 4. A pressure channel 10' transmits a reduced pressure on the valve. The construction of this valve and the passageways leading to it (FIGS. 3 and 4) at both ends have been heretofore known, except for the coactio-n with the novel passageway comprising channels 14 and 17 which effect an outlet bypass port for the valve, bypassing flow from pump outlet to pump inlet when the valve opens. The outer face of the valve piston is exposed to outlet pressure as will be evident from FIG. 3, while the reduced central portion of the valve communicates with bore 13 and channel 14. Channel 14 is not completely circular but has a side channel 17 (FIG. of approximately half the diameter of channel 14 to form a prebypass channel in relation to the bore 14 which forms a bypass channel. Obviously, channels 14 and 17 can be readily provided by boring.

It will be noted from FIGURE 5 that the configuration of the channels 14 and 17 is roughly that of an equilateral triangle wherein the apex formed by the pre-bypass channel 17 is generally directed toward the apex of the streamlined shape of the support segment 12 in its position with respect to the stator 5. By comparison of FIGURES 1 and 5 it will be seen that flow coming upwardly through channels 14 and 17, after valve opens, will be divided by the segment 12 so as to flow clockwise and counterclockwise around the stator and in the intake chambers 8' and 8, respectively. This dividing of the fiow produces a uniformity of filling of the intake chambers and in conjunction with the particular effect and coaction of the channels 14 and 17, substantially reduces or eliminates cavitation at high speeds.

Referring to FIG. 3, as the speed of the pump increases the outlet pressure will push the valve piston to the right and initially open up the pre-bypass channel 17 so that fluid from the pump outlet passages will flow initially into the inlet passages, mingling with inlet fluid from conduit 13. However, as speed increases, the valve 10 will open increasingly so that a heavier bypass flow via bypass channel 14 will take place. All such flow mingles with the inlet flow from suction channel 13 and is divided by the streamlined segment 12 around the stator so as to provide filling uniformity of the suction chambers.

An unexpected phenomenon takes place by virtue of the existence of the pre-bypass channel 17. Thus where a single circular base channel such as 14 is used, the bypass flow is not proportional to the differential pressure acting on the valve and this causes turbulence and pressure losses so that the intake pressure is not suflicient to avoid cavitation, and complete filling of the suction chambers is not achieved. However, by providing the pre-bypass channel 17 in conjunction with the flow divider segment 12 there is a control of flow initially which will maintain the intake pressure proportional to pump speed. Thus, as has been previously mentioned, the most ideal condition would be a bypass bore having the cross-section of an equilateral triangle so that upon increased bypass flow there will be a constant relationship with a difierential pressure Ap acting on the control valve 10. However, by the provision of the pre-bypass channel 17 the degree of opening with increase of pump speed is such that the differential pressure becomes where c is a constant and Q is the open valve area through which bypass flow takes place at a specific value position.

The above relationship holds generally true for composite channels of the type illustrated by channels 14 and 17 wherein the pre-bypass channel 17 is positioned so that if it were the apex of an equilateral triangle it would diverge in the direction of opening of control valve 10, as will be apparent from comparisn of FIGURES 3 and 5.

By providing a construction such as above described, the drawbacks of using a circular cross section channel as has been known in the prior art are overcome and by providing a constant relationship between the pressure differential acting on the control valve and the cross sectional opening of the valve for permitting bypass in proportion to pressure differential, there is substantial elimination of cavitation at all speeds.

The performance of the pump is illustrated in the graph of FIGURE 6 wherein the performance of a conventional pump is indicated by the line I, the inlet pressure being the ordinate in terms of atmospheres and the pump speed being in terms of revolutions per minute. The test conditions provide for an average outlet pressure of 50 atmospheres. Curve II illustrates the improved performance in terms of higher intake pressures where the pre-bypass channel 17 has been provided in a pump which utilizes dowel pins to support the stator but does not have the support segments, particularly the flow dividing segment 12. Curve III illustrates the further improvement where the flow divider segment 12 is utilized in conjunction with the pro-bypass channel 17.

The relative sizes of components and passages as shown on the drawing is for purposes of illustration. Thus, the actual design would depend on the particular application to which the pump is to be put. For example, the axial length of the bypass channel means comprising channels 14 and 17 might be 20% to 70% of the axial width of the cam ring. Likewise, a 10% to 50% axial length of the flow divider segment 12 may be used. Under some circumstances an even greater range of axial width for the channel means or flow divider may be utilized; e.g., 20% for the channel means and 60% for the flow divider.

We claim:

.1. A rotary vane pump having a housing and a cam ring and rotor therein, said housing having an inlet passage and an outlet passage, a pressure responsive bypass valve connected so as to be actuated by a pressure differential in response to pump speed for bypassing flow to said inlet passage from said outlet passage, a bypass channel means effecting an outlet port for said valve and connecting said valve to said inlet passage; said bypass channel means having a cross section transversely of fiow in a contour affording an apex of open area as said valve opens wherein said apex diverges in the direction of opening of said valve.

2. A rotary vane pump as set forth in claim 1, said bypass channel means comprising a merging of two circular bores to effect the approximate contour of an equilateral triangle, one bore being approximately half the diameter of the other bore and being joined thereto generally on a diameter of said one bore and effecting said apex.

3. A rotary vane pump as set forth in claim 1, said rotary vane pump having inlet chambers enveloping a portion of respective radial faces of said cam ring and extending around respective portions of the periphery of said cam ring; a fiow dividing element disposed to protrude axially of said cam ring exteriorly thereof and intermediate the peripheral portions of said inlet chambers; said bypass channel means terminating intermediate the peripheral portions of said inlet chambers, the apex of said bypass channel means diverging in the direction of said flow divider element and directing flow from said apex toward said flow divider element whereat flow is peripherally divided around said cam ring in opposite directions into said inlet chambers.

4. A rotary vane pump as set forth in claim 1, said bypass channel means comprising a merging of two circular bores to effect the approximate contour of an equilateral triangle, one bore being approximately half the diameter of the other bore and being joined thereto generally on a diameter of said one bore and effecting said apex, said rotary pump having inlet chambers enveloping a portion of respective radial faces of said cam ring and extending around respective portions of the periphery of said cam ring; a flow dividing element disposed to protrude axially of said cam ring exteriorly thereof and intermediate the peripheral portions of said inlet chambers; said bypass channel means terminating intermediate the peripheral portions of said inlet chambers, the apex of said bypass channel means diverging in the direction of said flow divider element so as to direct flow therefrom toward said flow divider element for dividing flow peripherally around said cam ring in opposite directions into said inlet chambers.

5. A rotary vane pump as set forth in claim 1, said rotary pump having inlet chambers enveloping a portion of respective radial faces of said cam ring and extending around respective portions of the periphery of said cam ring; a flow dividing element disposed to protrude axially of said cam ring exteriorly thereof and intermediate the peripheral portions of said inlet chambers; said bypass channel means terminating intermediate the peripheral portions of said inlet chambers, the apex of said bypass channel means diverging in the direction of said flow divider element so as to direct flow therefrom toward said flow divider element for dividing flow peripherally around said cam ring in opposite directions into said inlet chambers, said -flow divider element comprising a tapered formation having an apex directed toward said apex of said bypass channel means.

6. A rotary vane pump as set forth in claim 5, said flow divider element effecting a spacer and support member between said housing and cam ring for supporting said cam ring.

7. A rotary vane pump as set forth in claim 6, said flow divider element extending approximately 10% to 50% the axial width of said cam ring; said bypass channel means comprising an open area exposed to the peripheral portions of said inlet chambers and extending for an axial distance of the Width of said cam ring of from 10% to 50%.

8. A rotary vane pump as set forth in claim 6, including at least two additional spacer and support members intermediate said housing and cam ring, whereby said cam ring is supported wholly by said spacers including said flow divider element, and means connecting said housing and cam ring to prevent rotation of said cam ring.

References Cited UNITED STATES PATENTS 2,544,988 3/1951 Gardiner et al. 103-135 2,853,023 9/1958 English 103-- 13-6 3,059,580 10/1962 'Farrell et al. 103-42 3,236,566 2/1966 Halsey 103-42 3,253,548 5/1966 Zeigler et al. 10342 3,311,064 3/ 1967 Eichele et a1 10 3-136 DONLEY J. STOCKING, Primary Examiner.

W. J. GOODLIN, Assistant Examiner.

US. Cl. X.R. 103-136. 

